1. Field of the Invention
The present invention relates to an in-core-monitor-guide-tube supporting apparatus.
2. Description of the Related Art
An in-core monitor guide tube is disposed in a reactor vessel to make it possible to measure neutron fluxes during the operation of a boiling-water reactor and the like. A plurality of in-core monitor guide tubes are disposed in the reactor vessel in a substantially cylindrical shape. Thus, the in-core monitor guide tubes are integrally fixed by a beam or the like to be able to acquire predetermined rigidity when the in-core monitor guide tubes are disposed. For example, in Japanese Patent Application Laid-Open No. 2000-187093, a neutron-flux-monitor-guide-tube supporting apparatus has a cantilever beam in which corrugated sections of a bent shape and beam sections are alternately formed and a clamp that can be fixed to the cantilever beam. A plurality of in-core monitor guide tubes are disposed in the corrugated sections and the clamp is fixed to the cantilever beam to straddle the in-core monitor guide tubes in this state. In this way, the neutron-flux-monitor-guide-tube supporting apparatus integrally supports the in-core monitor guide tubes. This makes it possible to, when a plurality of in-core monitor guide tubes are disposed in a reactor vessel, improve rigidity of the in-core monitor guide tubes.
However, although the in-core monitor guide tubes are disposed between a bottom surface and a core support plate in the reactor vessel, some in-core monitor guide tubes are disposed between a top cover and the core support plate in the reactor vessel. Since control-rod guide tubes are provided in this section in the reactor vessel, a space for arranging the in-core monitor guide tubes is limited. When the in-core monitor guide tubes are disposed between the top cover and the core support plate in the reactor vessel, the in-core monitor guide tubes may have to be reduced in diameter. In this case, it is likely that the in-core monitor guide tubes have lower strength against vibration.